<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <form action=""></form>
  <script>
    ///api/addUser
    let fd = { data: '年后' }
    var xhr = new XMLHttpRequest()
    xhr.open('POST', 'http://localhost:3000/api/addUser')
    xhr.send(fd)
    xhr.onreadystatechange = function () {
      if (xhr.readyState === 4) {
        if (xhr.status === 200) {
          console.log(xhr.responseText);
        } else {
          console.log('出错');
        }
      }
    }
    xhr.upload.onprogress = function (event) {
      if (event.lengthComputable) {
        let precent = Math.floor(event.loaded / event.total * 100)
        console.log(percent);
      }
    }
  </script>
</body>

</html>